(1) Field of the Invention
The present invention relates to a display apparatus mounted on office automation machinery such as the word processor, personal computer, electronic typewriter and the like, and particularly a display apparatus for use on compact office automation machinery.
(2) Description of the Prior Art
Office automation machinery such as the word processor, personal computer, electronic typewriter and the like have made rapid progress in recent years as the central instrument for streamlining office work.
In particular, demands for compact machinery are increasing today and the CRT display which takes up a large installation space is being replaced by flat panel type displays requiring less space. Known panel type displays include a liquid crystal display, an EL display utilizing electroluminescence, and a plasma display utilizing discharge of plasma gas. These panel type displays have a smaller number of dots on the screen and therefore show a smaller number of characters per screen than the CRT display.
The latest office automation machinery of a relatively sophisticated class offer a diversified range of mode choice. Some of them are equipped with functions including a split screen mode wherein the screen is divided into two or more sections to allow editing work to be carried out on each screen section independently, and a help menu mode wherein handling methods are called to the screen when the operator forgets how to operate the machine. For these display modes it is desirable to have a large number of characters displayed on the screen.
As means for increasing the number of characters displayed, it is conceivable to reduce the size of characters and increase the number of lines thereby to increase the number of characters displayed per screen. A uniform increase in the number of lines would reduce the size of characters to an extent that the operator has difficulties in recognizing the characters, which constitutes a new drawback.
In order to eliminate this problem, it is desirable for the above panel type display to include means for varying the number of characters per screen according to purpose.
One of such means is to rewrite character code data stored in the video RAM. However, this would entail the problem of complication in software processing and high cost.